The autumn wind tickles the crab's feet, and it is time to eat crabs again.
But I'm sorry, this year's Mid-Autumn Festival, hairy crabs may disappoint you -
"High temperature hungry skinny hairy crab", "hairy crab will be absent from the Mid-Autumn Festival no matter how hard it is"... What's going on?
What are the effects of high temperatures on hairy crabs?The Chinese official name of the hairy crab is "Chinese river crab" (Eriocheir sinensis), which is found in many rivers and lakes on the mainland.
Regarding the origin of the name "hairy crab", there is a saying that in the past, fishermen would directly boil and eat this crab after catching it, and this cooking method in Wu language is called "煠 (zhá)", so it is called "crab", which later evolved into "hairy crab" in the process of circulation.
There is also a saying that because before catching crabs, they must first build a large gate with bamboo branches and straw, lay a net on the side of the gate, light up the horse lamp at night, and the crab group in the lake is tempted to swim to the gate and throw it into the net, so it is called "hairy crab".
Hairy crabs can survive in the temperature range of 5 °C to 30 °C, the most suitable temperature is 20 °C -25 °C, when the temperature is higher than 30 °C, hairy crabs will have symptoms such as anorexia, joint weakness, motor weakness, and growth retardation. If the temperature is higher than 35°C, they hardly eat, only consume the original energy in the body, and have no strength to molt. However, for arthropods such as hairy crabs, they need to fade their shells 5 times during the growth cycle to achieve the optimal size for consumption.
In the natural environment, animals will find ways to avoid bad weather to reduce their impact on themselves, such as going to deep water areas, or burrowing into the mud at the bottom of the river to avoid high temperatures, but the vast majority of the hairy crabs we eat are artificially farmed, and the crab ponds are mostly cement ponds, so it is difficult to "escape the heat" by transferring or digging holes
Understanding the living habits of hairy crabs, and comparing the high temperatures of Hubei, Hunan, Jiangsu and other places as the main production areas of hairy crabs this summer at more than 40 ° C, it is not difficult to understand why their body size has "shrunk" this year and the time to market has been delayed.
The national average temperature this summer (June 1 to August 31) was 22.3 °C, 1.1 °C higher than the same period of the year, the highest in the same period of history since 1961 when there were complete meteorological observation records. Image source: Weibo @ China Weather
Distribution of extreme heat days throughout the country. Image source: Weibo @ China Weather
Excessively high temperatures will not only affect the hairy crabs themselves, but also affect their living environment.
The aquatic grasses released in the crab pond are not only the feed of hairy crabs, but also shade and purify the water quality of hairy crabs, but the aquatic grasses are not tolerant to high temperatures and are easily decayed.
At the same time, the high temperature is easy to make the number of plankton in the water surge, in the larger water body may cause the impact is not obvious, but in the crab pond such a small and relatively closed water body environment, the large number of plankton may consume a large amount of oxygen in the water, resulting in lack of oxygen in the water, affecting the growth of hairy crabs, serious may lead to the death of hairy crabs.
Moreover, hairy crabs are very afraid of heat during transportation, if you look closely, you will find that the mail crabs will use plastic foam incubators, which also add several ice packs to maintain the temperature and humidity in the box during transportation to avoid crab death. The continuous high temperature weather also increases the loss of hairy crabs during transportation.
Of course, rising temperatures are not the only reason for the changes in the hairy crab market, and another important reason is that there is less precipitation in the south this year.
High temperatures and less rain have reduced the amount of water in many lakes and rivers, and the area of water bodies has also been greatly reduced. For example, the water level in some areas of Dongting Lake has reached the lowest level in the same period of history, 7.82 meters lower, and the water body area of Poyang Lake has shrunk by nearly 90% compared with the same period last year, and other waters in the middle and lower reaches of the Yangtze River have also had a greater impact.
In this case, the water surface that can provide for the cultivation of hairy crabs will be reduced, and the reduction in the production of hairy crabs will be the result of certainty.
This year, the precipitation in the Yangtze River Basin (358.9 mm) was 32.5% less than the same period of the year, the lowest in the same period of history since 1961, and the precipitation in the Taihu Lake Basin (296.8 mm) was 47.3% less than the same period of the year, the fourth least in the same period of history. Image source: Weibo @ China Weather
This year's high temperatures have also affected marine crabs.
Common sea crabs mainly include three-wart pike crab, distant sea pike crab, red star pike crab, Japanese crab, rusty spotted crab and so on. Unlike hairy crabs, these marine crabs are mainly derived from fishing, and the current catch in Zhoushan, Shengsi and other areas is less than 80% of last year's, and the quality is not as good as the same period last year.
The high temperature also increases the loss of these sea crabs in transit, further raising the "crab price".
How can I pick a delicious hairy crab?In the face of the price of hairy crabs this year, it can be said: "Hairy crabs, it is not easy to say that I love you." ”
But if you still want to have a full meal, how can you not "crab money and wealth"? It is important to master the selection method of hairy crabs.
We know that the delicious taste of hairy crab, in addition to crab meat, is mainly derived from "crab yellow" and "crab paste". The "crab yellow" of the female crab is the orange-yellow liver pancreas and the orange-colored gonads (ovaries), and the "yellow" of the male crab is the liver pancreas. "Crab paste" is the paragonad.
There are two important indicators that affect the flavor of hairy crabs: fullness and sweetness.In layman's terms, fullness refers to the amount of meat and yellow, while sweetness is the flavor of meat and yellow. High-quality hairy crabs, yellow and cream are sweet to eat, while crabs with poor quality will have a salty or bitter taste.
The fullness of hairy crabs can be guaranteed by eating enough plant-based feed, but the sweetness must be supplemented by animal food.
In order to ensure the taste of hairy crabs this year and minimize the impact of temperature, crab farmers are also trying their best:
For example, in the crab pond, reeds, black algae, ileum, bitter grass and other aquatic plants, plants can reduce the temperature of some water bodies in the pond and provide shelter and shelter for hairy crabs. By strengthening the water circulation of the crab pond to reduce the temperature of the water body in the crab pond, install an aerator, and increase the oxygen content of the water in the crab pond and promote the water cycle by stirring.
After such a "toss", the condition of the hairy crabs in the pond will improve.
Before the hairy crab is listed, crab farmers will also ensure the sweetness of hairy crabs by feeding a large number of animal baits such as fish, shrimp, snails, river mussels and so on.
Here to share with you a method of picking hairy crabs -
Hairy crabs in good condition have four major characteristics: One is the green back, the crab shell appears cyan, smooth and shiny; The second is the white belly, the mud-covered umbilical carapace, crystal white; The third is yellow hair, the hair of the crab leg is long and yellow, and the roots are straight; The fourth is the golden claw, the crab claw is golden, solid and powerful.The crab in the hand, to have a heavy feeling, such a crab will be full and not empty. You can also turn the crab without a rope over, the belly is facing up, if the crab can quickly turn over and move flexibly, it means that the crab is full of vitality and freshness.
The continued heat does cause us a lot of trouble eating crabs, but some meteorologists believe that sustained high temperatures like this year will not become the norm, and maybe next year we will be able to continue to eat crabs happily.
Of course, in order to be able to eat "good crabs" that are both fat and cheap all the time, each of us also tries our part to protect the environment.
(Popular Science China WeChat public account)